Vehicles such as automobiles, trucks, busses, trains and aircraft typically employ internal combustion engines which produce significant heat. Components of an engine, such as the exhaust manifold, catalytic converter and exhaust pipe, can achieve temperatures of several hundred degrees during the normal course of engine operation. These hot components must often be placed in proximity to other components, such as brake lines, electrical wiring or fuel lines, which must remain cool for long-term, effective operation. For example, if unprotected brake lines are located next to the exhaust pipe of an automobile, the brake fluid can be heated and vaporized within the lines. This can lead to a loss of hydraulic pressure and brake failure. Similarly, if unprotected wiring passes near a hot engine component, the electrical insulation could melt and/or ignite, causing an engine fire and an electrical short circuit. If a fuel line is heated sufficiently by an adjacent engine component, gasoline in the line will vaporize leading to a complete or partial interruption of fuel flow to the engine. This is known as vapor lock, and under extreme conditions of vapor lock, the engine will stop or will not start.
Although the problems listed above can often be avoided by keeping hot components sufficiently distant from components which must remain cool, this is not always practical and can lead to more expensive designs and undesirable design tradeoffs. It is, therefore, desirable to provide thermal protection for elongated components, such as brake lines, wiring harnesses, fuel lines and the like, from the consequences of extreme heat of some engine components.